Ghost update: how to delete it?

This is sounding like you have a pirated app which is using the recipt of another.

Just in case it's something else going on here, could you try searching for that name in the spotlight to make sure someone hasn't installed that app somewhere you do not expect?

You see an update, what happens when you try to update the app in question? Does a stranger's Apple ID appear in conjunction with attempts to update the app?

A stranger's Apple ID appears on your Mac in conjunction with an update notice

OK, I dl FAF but it did not find that "fake user ID" on my Mac and I think it'd be a bit long and tiresome to find it app by app.

You have a pirated app on your Mac. The only way to get rid of the update is to delete the pirated app. You either haven't understood the process outlined in the link or just don't want to do the work. It should be easy, you know the apps you downloaded from an outside source, whether you intentionally installed a pirated app or installed an app you believed was a trial version of a paid app in the MAS.

You're stuck with your issue until you are willing to do the work to eliminate it. There is no shortcut or alternative.

You either haven't understood my question or just don't want to answer (about How to delete unwanted updates, whether they are for pirated apps or useless things whatsoever).

Why would I waste my time here (I run a very successful business in Mexico) if I had a shortcut solution to your issue but was refusing to give it to you. That would be stupid.

The reason there is no cheap, fast & dirty, conventional solution is because this is not a conventional problem. You did not download this app from the MAS. You don't have the actual app that is calling for the update. You have that app's MAS receipt hidden inside the app bundle of a pirated app that you installed. Because of that this app does not appear in your Purchased list. If it did, the solution would as easy as hiding the purchase and that would stop the notice of update.

This is not an app that you downloaded a long time ago, unless you have had this issue a long time. If this recently appears, then it is likely due to an app you installed recently.

You have been given the only solution. I am the resident expert on the issue, no one else will have anything else to offer.

Ciao

It's the first (and probably last) time I use MAS

As I just stated, your issue is not because you downloaded an app from the MAS.

But, again, you did not answer my question: Is there a way I can delete undesired updates (ANY update!)?

To remove updates for MAS apps that you have actually downloaded from the MAS, signing into your account and hiding the app in question in the MAS Purchases pane will stop the update notice.

Duromac, could you let me know the EXACT Apple ID that pops up on the update popup? This may help to locate which app is causing this, and I'd like to put it down in my reccords of pirated apps for future reference.

Thanks.